On the B737, the FDs command 15 degrees pitch up during takeoff roll above 64/84 knots and then revert to the normal speed function after liftoff.
Two points:
1. FDs are NOT to be used for any kind of rotation guidance. Disregard them until airborne.
2. You can't always see the pitch the FD is commanding. It only shows you the direction to which you need to pitch to satisfy the command and how close you are to the target pitch attitude. I.e. if you pitch to -5 deg on takeoff, you will still see the pitch FD bar, despite the target will probably be 20+ deg, which you won't be able to see on the attitude indicator.